The present invention relates to a method and apparatus for thermo-magnetically recording information data by applying thermal energy of convergent rays (e.g. a laser beam) to a magnetic layer within a magnetic field and/or reproducing the recorded information data on the basis of magneto-optical effect (referred to as magneto-optical recording/reproducing, thereinafter).
Recently, magneto-optical recording technique adopting a perpendicular magnetized film as a recording medium has been widely researched as one of optical rewritable recording methods and has been already put into practical use. In this method, information data are recorded thermo-magnetically. In more detail, an energy beam such as a constant or pulse-modulated laser beam is focused onto a memory layer within a modulated or static magnetic field to heat the memory area, so that switched magnetic domains can be formed in the memory layer according to information data, in dependence upon the magnetic interaction between the memory layer and the external field, to record information data.
In the prior-art recording technique, however, there exists a problem in that switched magnetic domain are erroneously formed or recorded magnetic domains are distorted in shape due to non-uniformity of the recording medium or focusing error, with the result that recording noise is inevitably generated and therefore the reproduced signal quality is deteriorated. Further, in the case of direct overwriting which needs no erasing operation separate from the recording operation, even though former domains are supposedly erased simultaneously with the recording of new domains over the former domains, in practice, vestiges of some of the former domains still remain as they have not been perfectly erased during the recording of the new domains.